This invention generally relates to porous tubing assemblies for catheters. More specifically, this invention relates to providing drainage catheters having an extremely fine pore structure. In an important aspect of the present invention, the extremely fine pore structure is formed by winding extruded polymer fibers onto a rotating mandrel. The wound porous portion may be bonded to a non-porous polymer tube thereby forming a tubing assembly for use in a system which drains excess cerebrospinal fluid (CSF) from a ventricle of the brain.
Systems for draining excess CSF are generally known in the art. Such systems, either for use on a temporary or substantially permanent basis, have been known and used for a number of years for the treatment of hydrocephalus. The more permanent types of systems generally include an implantable valve which allows the CSF to pass from the ventricle of the brain to a suitable drainage location within the body. Such valves are actuated by displacing an internal diaphragm or the like in response to applied pressure differentials thereby regulating the passage of CSF from the ventricular spaces, through the catheter and on to the drainage location. An example of such a valve can be found in U.S. Pat. No. 4,557,721, the disclosure of which is incorporated by reference herein.
Similar types of ventricular catheters are included in temporarily implanted intracranial drainage, monitoring, and/or injection systems which gain access to the ventricular spaces through a flexible ventricular catheter. Illustrative of such temporarily implanted systems is a system as shown in FIG. 2 of U.S. Pat.No. 4,601,724, the disclosure of which is incorporated by reference herein.
Because of the delicate nature of the brain tissue with which the catheter comes into contact, it is desirable that the tubing assembly which comprises the ventricular catheter be manufactured from flexible materials. The catheter, in addition to being flexible, contains a multitude of inlet holes or pores through which the CSF flows. A recognized problem in the art of ventricular catheters has been the problem of pore blockage caused by the ingrowth of the choroid plexus, ventricular collapse over the catheter pores, hemorrhage, and the like. Those skilled in the art have attempted to solve the problem of pore blockage in different ways. One such approach to the problem has focused on increasing the number of inlet holes or pores through which the CSF may pass into the catheter tubing. One such effort is illustrated in U.S. Pat. No. 4,601,724, mentioned above, describing a polymeric tubing assembly which includes a length of tubing having micro-orifices which are ion sputtered therethrough.
Other efforts, such as that described in U.S. Pat. Re. No. 27,310 by Hakim, have taken different approaches to the problem of pore blockage. Hakim, for example, uses a finned catheter comprising flexible membranes extending radially outward from the porous catheter tubing. These flexible membranes will bend to cover and protect the pores when contacted by tissue from the choroid plexus and the like.
The present invention provides a ventricular catheter which possesses the desired properties of small pore size with a maximal number of pores through which CSF may pass. The method and product produced thereby include providing a length of polymeric tubing assembly comprising a non-porous tubular portion bonded to a porous tubular portion. In the embodiment described herein, the porous portion typically forms roughly the distal one-third portion of the catheter tubing assembly and is bonded to the non-porous portion by heat or solvent reformation of the associated ends of the two portions. The porous portion is generally formed by extruding a fiber forming polymer, such as polyurethane, which is wound directly onto a rotating mandrel. One approach for manufacturing a porous tubular structure, suitable for use as vascular grafts, is detailed in U.S. Pat. No. 4,475,972, the disclosure of which is incorporated by reference herein.
Once the porous tubular portion and the non-porous tubular portion are bonded together, the free floating open end of the porous portion is closed, generally by heat or solvent reformation. In this manner, a tubing assembly suitable for use as a ventricular catheter is provided which includes a highly porous portion that is substantially resistant to blockage under in vivo conditions.
It is accordingly an object of the present invention to provide an improved catheter assembly.
Another object of this invention is to provide an improved method for manufacturing a tubing assembly having a porous portion formed by winding extruded polymer fibers onto a rotating mandrel.
Another object of the present invention is to provide an improved method and product produced thereby which takes advantage of the improved porosity of tubing made by winding extruded polymeric fibers onto a rotating mandrel.
These and other objects of the present invention will be apparent to those skilled in the art from the following.